scholarly journals Spatial-temporal variations and their dynamics of the saline lakes in the Qaidam Basin over the past 40 years

2016 ◽  
Vol 46 ◽  
pp. 012043
Author(s):  
S L Zhou ◽  
W C Zhang ◽  
F Wang
Keyword(s):  
Saline Lakes ◽  
Qaidam Basin ◽  
Temporal Variations ◽  
The Past

Seasonal deposition of phytodetritus to the deep-sea floor

1986 ◽  
Vol 88 ◽  
pp. 265-279 ◽  
Author(s):  
A. L. Rice ◽  
D. S. M. Billett ◽  
J. Fry ◽  
A. W. G. John ◽  
R. S. Lampitt ◽  
...  
Keyword(s):  
Deep Sea ◽  
Benthic Communities ◽  
Time Lapse ◽  
Sediment Traps ◽  
Temporal Variations ◽  
Sea Floor ◽  
Porcupine Seabight ◽  
The Past ◽  
Sea Bed ◽  
Seasonal Deposition

SynopsisEvidence has accumulated over the past twenty years to suggest that the deep-sea environment is not as constant as was at one time thought, but exhibits temporal variations related to the seasonally in the overlying surface waters. Recent results from deep-moored sediment traps suggest that this coupling is mediated through the sedimentation of organic material, while observations in the Porcupine Seabight indicate that in this region, at least, there is a major and rapid seasonal deposition of aggregated phytodetritus to the sea-floor at slope and abyssal depths.This paper summarises the results of the Porcupine Seabight studies over the past five years or so, using time-lapse sea-bed photography and microscopic, microbiological and chemical analyses of samples of phytodetritus and of the underlying sediment. The data are to some extent equivocal, but they suggest that the seasonal deposition is a regular and dramatic phenomenon and that the material undergoes relatively little degradation during its passage through the water column. The mechanisms leading to the aggregation of the phytodetritus have not been identified, and it is not yet known whether the phenomenon is geographically widespread nor whether it is of significance to the deep-living mid-water and benthic communities.

scholarly journals Spatio-temporal variations of the major meteorological disasters and its response to climate change in Henan Province during the past two millennia

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12365
Author(s):  
Xiang Li ◽  
Hui Lu ◽  
Zhaokang Zhang ◽  
Wei Xing
Keyword(s):  
Low Temperature ◽  
Correlation Analysis ◽  
Natural Disasters ◽  
Temporal Variations ◽  
Henan Province ◽  
Historical Documents ◽  
The Past ◽  
Meteorological Disaster ◽  
Spatio Temporal ◽  
Meteorological Disasters

In China, historical documents have recorded large quantities of information related to natural disasters, and these disasters have had long-lasting effects on economic and social activities. Understanding the occurrence of the natural disasters and their spatio-temporal variation characters is crucial for sustainable of our society. Therefore, based on the collection and collation of historical documents, and adopting mathematical statistics, Kriging interpolation, correlation analysis and other methods, we systematically explored the meteorological disasters in Henan Province during the past two millennia in analyzing their spatio-temporal distribution characters and driving forces. The results demonstrate that there were five major types of meteorological disasters in Henan Province, including drought, flood, hails, low temperature and frost and insect pests, which presented obvious spatio-temporal variations and have occurred frequently during the past two millennia. According to the historical documents, the major meteorological disasters occurred 1,929 times in Henan from 221 BCE to 2000 CE. On the whole, the disaster frequency show that the occurrence cycle of the meteorological disasters has obvious changes, which mainly occurred in the middle and late stages during the past two millennia, especially after 1300 CE. Furthermore, we also find that the variation of meteorological disaster events is consistent with the variation of temperature in eastern China and the frequency of meteorological disaster increases in the cold period, but decreases in the warm period. In addition, there are obvious differences in the spatial distribution of the major meteorological disaster, which were mainly distributed in the northwest and southern part region of the Henan Province before 1911 CE. While after 1911 CE, the northern and southeastern parts were the meteorological disaster-prone areas in this region during this period. Spatial correlation analysis of each meteorological disaster before and after 1911 CE points out the droughts disaster frequency-occurring district has transferred in different periods, while the hail and low temperature and frost disasters just have a smaller transferred during these two periods. Conversely, the frequency-occurring districts of floods and insect pest disasters have no obviously transferred in different periods. These results can provide an important scientific basis for governmental decision makers and local people to prevent and mitigate meteorological disaster in the future.

scholarly journals Distribution Characteristics and Influencing Factors of Uranium Isotopes in Saline Lake Waters in the Northeast of Qaidam Basin

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 74
Author(s):  
Chen Zhao ◽  
Pu Zhang ◽  
Xiangzhong Li ◽  
Youfeng Ning ◽  
Liangcheng Tan ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Saline Lakes ◽  
Natural Waters ◽  
Qaidam Basin ◽  
Influencing Factor ◽  
Dominant Factor ◽  
Uranium Isotopes ◽  
Distribution Characteristics ◽  
Total Dissolved Solid ◽  
Lake Waters

Four saline lakes in the northeast of Qaidam Basin were selected to explore the distribution characteristics and influencing factors of uranium isotopes in lake waters with high evaporation background. The 238U concentration and the activity ratios of 234U/238U ([234U/238U]AR) showed that there was no significant change in the same lake, but there was a certain degree of difference in the distribution between different lakes. We found that aqueous 238U concentration within a certain range increased with an increase in TDS (total dissolved solid) and salinity, as was also the case with pH. As in natural waters, the pH affects the speciation of 238U, but TDS and salinity affect the adsorption process of aqueous 238U. Further, the replenishment of water will also affect the uranium isotope concentration for lakes, but it is not the main influencing factor for saline lakes. Therefore, we suggest that pH is the dominant factor affecting changes in aqueous 238U concentration of the sampled saline lakes. The [234U/238U]AR in these saline lakes are closely related to the input water and the associated water–rock interactions involving sediments, atmosphere dust, and organic material, etc. during the evolution stage, metamorphous degree, and hydrochemistry of the saline lakes. Lake water samples collected in the maximum and minimum discharge water period, were used to evaluate the seasonal distribution characteristics of aqueous 238U, and we found that 238U concentration did not show an evident change with the seasons in these saline lakes. If the 238U concentration and [234U/238U]AR can remain consistent during a period of time, then the sediment ages and/or sedimentation rates could be determined by lake sediment and/or biogenic carbonate in future, thus allowing for the accurate reconstruction of the paleoclimate and paleoenvironment.

Coupled supercontinent–mantle plume events evidenced by oceanic plume record

Geology ◽  
2019 ◽  
Vol 48 (2) ◽  
pp. 159-163 ◽  
Author(s):  
Luc S. Doucet ◽  
Zheng-Xiang Li ◽  
Richard E. Ernst ◽  
Uwe Kirscher ◽  
Hamed Gamal El Dien ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Shear Velocity ◽  
Temporal Variations ◽  
Large Igneous Provinces ◽  
First Order ◽  
The Past ◽  
Igneous Provinces ◽  
Island Basalt ◽  
Supercontinent Cycle ◽  
Low Shear

Abstract The most dominant features in the present-day lower mantle are the two antipodal African and Pacific large low-shear-velocity provinces (LLSVPs). How and when these two structures formed, and whether they are fixed and long lived through Earth history or dynamic and linked to the supercontinent cycles, remain first-order geodynamic questions. Hotspots and large igneous provinces (LIPs) are mostly generated above LLSVPs, and it is widely accepted that the African LLSVP existed by at least ca. 200 Ma beneath the supercontinent Pangea. Whereas the continental LIP record has been used to decipher the spatial and temporal variations of plume activity under the continents, plume records of the oceanic realm before ca. 170 Ma are mostly missing due to oceanic subduction. Here, we present the first compilation of an Oceanic Large Igneous Provinces database (O-LIPdb), which represents the preserved oceanic LIP and oceanic island basalt occurrences preserved in ophiolites. Using this database, we are able to reconstruct and compare the record of mantle plume activity in both the continental and oceanic realms for the past 2 b.y., spanning three supercontinent cycles. Time-series analysis reveals hints of similar cyclicity of the plume activity in the continent and oceanic realms, both exhibiting a periodicity of ∼500 m.y. that is comparable to the supercontinent cycle, albeit with a slight phase delay. Our results argue for dynamic LLSVPs where the supercontinent cycle and global subduction geometry control the formation and locations of the plumes.

scholarly journals Asymmetry in the periodicities of solar photospheric fields: A probe to the unusual solar minimum prior to cycle 24

2012 ◽  
Vol 8 (S294) ◽  
pp. 85-86
Author(s):  
Susanta Kumar Bisoi ◽  
P. Janardhan
Keyword(s):  
Solar Minimum ◽  
Temporal Variations ◽  
Solar Observatory ◽  
Fourier Methods ◽  
Latitude Range ◽  
The Past ◽  
National Solar Observatory ◽  
Cycle 24 ◽  
South Asymmetry ◽  
Inner Heliosphere

AbstractEmploying wavelet and Fourier methods, we investigate temporal variations of periodicities in the photospheric fields obtained from synoptic magnetograms of the National Solar Observatory at Kitt Peak (NSO/KP) spanning the years 1975-2009. A north-south asymmetry is noticed in the periodicities of photospheric fields in the latitude range, 45°-78°, when the data is grouped into fields prior to and after 1996. This asymmetry when coupled with the fact that both solar fields in the latitude range, 45°-78°, and the micro-turbulence levels in the inner heliosphere began declining ~ 1995-1996 suggests that active changes occurred in the underlying basic solar processes which eventually initiated, at the end of solar cycle 23, the build-up of the deepest solar minimum, in the past 100 years.

scholarly journals Glasgow University Radiocarbon Measurements III

Radiocarbon ◽  
1970 ◽  
Vol 12 (2) ◽  
pp. 496-502 ◽  
Author(s):  
M. S. Baxter ◽  
A. Walton
Keyword(s):  
Temporal Variations ◽  
Past Century ◽  
Annual Variations ◽  
The Past

The following list presents results obtained during 1968-69 on a series of samples chosen to investigate temporal variations of C14 concentrations in the atmosphere during the past century. Together with data presented previously (Radiocarbon, 1969, v. 11, p. 45-52) they constitute a study of annual variations of C14 activities at N temperate latitudes.

Distinct co-occurrence patterns of prokaryotic community between the waters and sediments in lakes with different salinity

2020 ◽  
Vol 97 (1) ◽  
Author(s):  
Jian Yang ◽  
Hongchen Jiang ◽  
Xiaoxi Sun ◽  
Jianrong Huang ◽  
Mingxian Han ◽  
...  
Keyword(s):  
Community Composition ◽  
Saline Lakes ◽  
High Salinity ◽  
Temporal Variations ◽  
Prokaryotic Community ◽  
Low Salinity ◽  
Topological Features ◽  
Phylogenetic Composition ◽  
Occurrence Patterns ◽  
Lake Waters

ABSTRACT Temporal variations and co-occurrence patterns of the prokaryotic community in saline lakes remain elusive. In this study, we investigated the temporal variations of the prokaryotic community in six lakes with different salinity by using Illumina sequencing. The results showed that prokaryotic community compositions exhibited temporal variations in all studied lakes, which may be partially caused by temporal fluctuations of environmental variables (e.g. salinity, temperature, total nitrogen). Salinity fluctuations exhibited stronger influences on temporal variations of prokaryotic community composition in the lakes with low salinity than in those with high salinity. Stochastic factors (i.e. neutral processes) also contributed to temporal variations of prokaryotic community composition, and their contributions decreased with increasing salinity in the studied saline lakes. Network analysis showed that prokaryotic co-occurrence networks of the studied lakes exhibited non-random topology. Salinity affected the phylogenetic composition of nodes in the studied networks. The topological features (e.g. average connectivity and modularity) of the studied networks significantly differed between lake waters and sediments. Collectively, these results expand our knowledge of the mechanisms underlying prokaryotic community assembly and co-occurrence relationships in saline lakes with different salinity.

Chemical Characterization of Saline Lake and Playa Salts in Qaidam Basin: Implications for Climates of Planet Earth and Mars

2021 ◽  
Author(s):  
Wanyu Liu ◽  
Jun Li ◽  
Luis Santos ◽  
Johan Boman ◽  
Xiying Zhang ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Saline Lakes ◽  
Saline Lake ◽  
Qaidam Basin ◽  
Chemical Characterization ◽  
Physicochemical Characteristics ◽  
Global Scale ◽  
Factors Affecting ◽  
Complex Chemical Composition ◽  
The Common

<p>Salt aerosol from saline lakes and playas has been recognized to affect climate in the global scale, but the understandings of the chemical and physical natures of these salts are still limited due to their complex chemical composition. The Qaidam Basin, one of the largest and driest deserts on Earth, is composed of many saline lakes and is regarded as a good terrestrial analogue for Mars due to similar environment conditions and elementary composition(Xiao et al., 2017). The study on the chemical characteristics of salts from Qaidam Basin is helpful to explore their influences on climate and reveal the physical and chemical factors affecting the paleoclimate of both Planet Earth and Mars.</p><p> </p><p>In this study, four types of salt samples (brines, crystalized brines, lakebed salts and crust salts) collected at and near four saline lakes (Chaka, Keke, Qarhan and Mang’ai) in the Qaidam Basin are studied for their physicochemical characteristics. The common cations (Na<sup>+</sup>, K<sup>+</sup>, Mg<sup>2+</sup> and Ca<sup>2+</sup>) and anions (Cl<sup>−</sup>, SO<sub>4</sub><sup>2−</sup>, and NO<sub>3</sub><sup>−</sup>) are determined by ion chromatography (IC), and the elemental compositions are measured by energy dispersive X-ray fluorescence (EDXRF) spectrometry. The chemical composition results are analyzed by positive matrix factorization (PMF)(Paatero and Tapper, 1994). The pH of sample brines and solutions are measured, and the governing factors are discussed.</p><p> </p><p>The common elements detected by XRF and IC have excellent consistency. Notably, the crystalized brines exhibit similar ionic compositions with brines, suggesting that the crystalized brines well reflect the complex mineral composition of brines and evaporative crystallization can be used for brine preservation. However, the natural solid salts (lakebed salts and crust salts) present obvious composition differences. Mg<sub>2</sub><sup>+</sup> and SO<sub>4</sub><sup>2-</sup> are primarily found in brines, while the natural solid salts are dominated by NaCl and KCl. The pH of the brines and salt solutions are found to correlate to Mg<sup>2+</sup> concentrations and potentially affected by ambient CO<sub>2</sub> uptake. The electrical conductivities of sample solutions are not linearly scaled by the dilution factors, indicating that balanced reactions and buffer systems exist in the salt textures. Three interpretable factors are identified by the PMF analysis, and the differences of sample types and sampling sites are clearly reflected by the three factors. The lakebed salts (except for the QH lakebed salt) presented excellently correlation with the crust salts, and the crystalized salts are greatly correlated with the brines. This study improves the understandings of the physiochemical features of saline lake and playa salts in Qaidam Basin, and the roles that surface salts potentially play in the climate systems of both Planet Earth and Mars are discussed.</p><p> </p><p><strong>Reference</strong></p><p>Paatero, P., and Tapper, U., Environmetrics, 5, 111-126, <strong>1994</strong>.</p><p>Xiao, L., Wang, J., Dang, Y., et al., Earth-Sci Rev, 164, 84-101, <strong>2017</strong>.</p>

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